Semi-rigid collapsible container

ABSTRACT

A semi-rigid collapsible container has a side-wall with an upper portion, a central portion, a lower portion and a base. The central portion includes a vacuum panel portion having a control portion and an initiator portion. The control portion is inclined more steeply in a vertical direction, i.e. has a more acute angle relative to the longitudinal axis of the container, than the initiator portion. On low vacuum force being present within the container panel following the cooling of a hot liquid in the container the initiator portion will flex inwardly to cause the control portion to invert and flex further inwardly into the container and the central portion to collapse. Raised ribs made an additional support for the container in its collapsed state. In another embodiment the telescoping of the container back to its original position occurs when the vacuum force is released following removal of the container cap.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of Ser. No. 11/413,583, filed Apr. 28, 2006, nowU.S. Pat. No. 8,047,389, which is a continuation of U.S. patentapplication Ser. No. 10/363,400, entitled “Semi-Rigid CollapsibleContainer”, filed Feb. 26, 2003, now U.S. Pat. No. 7,077,279, which is a371 application of PCT/NZ01/00176, filed Aug. 29, 2001, which claimspriority from New Zealand patent application entitled, “Semi-RigidCollapsible Container”, filed on Aug. 31, 2000, Application No. 506684;and New Zealand application entitled, “Semi-Rigid CollapsibleContainer”, filed on Jun. 15, 2001, Application No. 512423, all of theforegoing of which are fully incorporated herein by reference and fromwhich the present application claims priority.

BACKGROUND TO INVENTION

This invention relates to polyester containers, particularly semi-rigidcollapsible containers capable of being filled with hot liquid, and moreparticularly to an improved construction for initiating collapse in suchcontainers.

‘Hot-Fill’ applications impose significant mechanical stress on acontainer structure. The thin side-wall construction of a conventionalcontainer deforms or collapses as the internal container pressure fallsfollowing capping because of the subsequent cooling of the liquidcontents. Various methods have been devised to sustain such internalpressure change while maintaining a controlled configuration.

Generally, the polyester must be heat-treated to induce molecularchanges resulting in a container that exhibits thermal stability. Inaddition, the structure of the container must be designed to allowsections, or panels, to ‘flex’ inwardly to vent the internal vacuum andso prevent excess force being applied to the container structure. Theamount of ‘flex’ available in prior art, vertically disposed flex panelsis limited, however, and as the limit is reached the force istransferred to the side-wall, and in particular the areas between thepanels, of the container causing them to fail under any increased load.

Additionally, vacuum force is required in order to flex the panelsinwardly to accomplish pressure stabilisation. Therefore, even if thepanels are designed to be extremely flexible and efficient, force willstill be exerted on the container structure to some degree. The moreforce that is exerted results in a demand for increased containerwall-thickness, which in turn results in increased container cost.

The principal mode of failure in all prior art known to the applicant isnon-recoverable buckling, due to weakness in the structural geometry ofthe container, when the weight of the container is lowered forcommercial advantage. Many attempts to solve this problem have beendirected to adding reinforcements to the container side-wall or to thepanels themselves, and also to providing panel shapes that flex at lowerthresholds of vacuum pressure.

To date, only containers utilising vertically oriented vacuum flexpanels have been commercially presented and successful.

In our New Zealand Patent 240448 entitled “Collapsible Container”, asemi-rigid collapsible container is described and claimed in whichcontrolled collapsing is achieved by a plurality of arced panels whichare able to resist expansion from internal pressure, but are able toexpand transversely to enable collapsing of a folding portion under alongitudinal collapsing force. Much prior art in collapsible containerswas disclosed, most of which provided for a bellows-like, oraccordion-like vertical collapsing of the container.

Such accordion-like structures are inherently unsuitable for hot-fillapplications, as they exhibit difficulty in maintaining containerstability under compressive load. Such containers flex their sidewallsaway from the central longitudinal axis of the container. Further,labels cannot be properly applied over such sections due to the verticalmovement that takes place. This results in severe label distortion. Forsuccessful label application, the surface underneath must bestructurally stable, as found in much prior art cold-fill containersidewalls whereby corrugations are provided for increased shaperetention of the container under compressive load. Such compressive loadcould be supplied by either increased top-load or increased vacuumpressure generated within a hot-fill container for example.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a semi-rigid container whichis able to more efficiently compensate for vacuum pressure in thecontainer and to overcome or at least ameliate problems with prior artproposals to date and/or to at least provide the public with a usefulchoice.

SUMMARY OF THE INVENTION

According to one aspect of this invention there is provided a semi-rigidcontainer, a side wall of which has at least one substantiallyvertically folding vacuum panel portion including an initiator portionand a control portion which resists being expanded from the collapsedstate.

Preferably the vacuum panel is adapted to fold inwardly under anexternally applied mechanical force in order to completely remove vacuumpressure generated by the cooling of the liquid contents, and to preventexpansion from the collapsed state when the container is uncapped.

According to a further aspect of this invention there is provided asemi-rigid container, a side wall of which has a substantiallyvertically folding vacuum panel portion including an initiator portionand a control portion which provides for expansion from the collapsedstate.

Preferably the vacuum panel is adapted to fold inwardly under a vacuumforce below a predetermined level and to enable expansion from thecollapsed state when the container is uncapped and vacuum released.

Further aspects of this invention, which should be considered in all itsnovel aspects, will become apparent from the following description.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1: shows diagrammatically an enlarged view of a semi-rigidcollapsible container according to one possible embodiment of theinvention in its pre-collapsed condition;

FIG. 2: shows the container of FIG. 1 in its collapsed condition;

FIG. 3: very diagrammatically shows a cross-sectional view of thecontainer of FIG. 2 along the arrows A-A;

FIG. 4: shows the container of FIG. 1 along arrows A-A;

FIG. 5: shows a container according to a further possible embodiment ofthe invention;

FIG. 6: shows the container of FIG. 5 after collapse;

FIG. 7: shows a cross-sectional view of the container of FIG. 6 alongarrows B-B;

FIG. 8: shows a cross-sectional view of the container of FIG. 5 alongarrows B-B;

FIGS. 9 a and 9 b: show expanded views of the section between lines X-Xand Y-Y of the container of FIG. 1 in its pre-collapsed and collapsedconditions respectively; and

FIGS. 10 a and 10 b: show expanded views of the same section of thecontainer of FIG. 1 in its pre-collapsed and collapsed conditionsrespectively, but with the ribs 3 omitted.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to collapsible semi-rigid containershaving a side-wall with at least one substantially vertically foldingvacuum panel section which compensates for vacuum pressure within thecontainer.

Preferably in one embodiment the flexing may be inwardly, from anapplied mechanical force. By calculating the amount of volume reductionthat is required to negate the effects of vacuum pressure that wouldnormally occur when the hot liquid cools inside the container, avertically folding portion can be configured to allow completely forthis volume reduction within itself. By mechanically folding the portiondown after hot filling, there is complete removal of any vacuum forcegenerated inside the container during liquid cooling. As there is noresulting vacuum pressure remaining inside the cooled container, thereis little or no force generated against the sidewall, causing lessstress to be applied to the container sidewalls than in prior art.

Further, by configuring the control portion to have a steep angle,expansion from the collapsed state when the container is uncapped isalso prevented. A large amount of force, equivalent to that mechanicallyapplied initially, would be required to revert the control portion toits previous position. This ready evacuation of volume with negation ofinternal vacuum force is quite unlike prior art vacuum panel containerperformance.

The present invention may be a container of any required shape or sizeand made from any suitable material and by any suitable technique.However, a plastics container blow moulded from polyethylenetetraphalate (PET) may be particularly preferred.

One possible design of semi-rigid container is shown in FIGS. 1 to 4 ofthe accompanying drawings. The container referenced generally by arrow Cis shown with an open neck portion 4 leading to a bulbous upper portion5, a central portion 6, a lower portion 7 and a base 8.

The central portion 6 provides a vacuum panel portion that will foldsubstantially vertically to compensate for vacuum pressure in thecontainer 10 following cooling of the hot liquid.

The vacuum panel portion has an initiator portion 1 capable of flexinginwardly under low vacuum force and causes a more vertically steeplyinclined (a more acute angle relative to the longitudinal axis of thecontainer 10), control portion 2 to invert and flex further inwardlyinto the container 10.

The provision of an initiator portion 1 allows for a steep, relative tothe longitudinal, angle to be utilised in the control portion 2. Withoutan initiator portion 1, the level of force needed to invert the controlportion 2 may be undesirably raised. This enables strong resistance toexpansion from the collapsed state of the bottle 1. Further, without aninitiator portion to initiate inversion of the control portion, thecontrol portion may be subject to undesirable buckling under compressivevertical load. Such buckling could result in failure of the controlportion to fold into itself satisfactorily. Far greater evacuation ofvolume is therefore generated from a single panel section than fromprior art vacuum flex panels. Vacuum pressure is subsequently reduced toa greater degree than prior art proposals causing less stress to beapplied to the container side walls.

Moreover, when the vacuum pressure is adjusted following application ofa cap to the neck portion 4 of the container 10 and subsequent coolingof the container contents, it is possible for the collapsing section tocause ambient or even raised pressure conditions inside the container10.

This increased venting of vacuum pressure provides advantageously forless force to be transmitted to the side walls of the container 10. Thisallows for less material to be necessarily utilised in the constructionof the container 10 making production cheaper. This also allows for lessfailure under load of the container 10, and there is much lessrequirement for panel area to be necessarily deployed in a design of ahot fill container, such as container 10. Consequently, this allows forthe provision of other more aesthetically pleasing designs to beemployed in container design for hot fill applications. For example,shapes could be employed that would otherwise suffer detrimentally fromthe effects of vacuum pressure. Additionally, it would be possible tofully support the label application area, instead of having a ‘crinkle’area underneath which is present with the voids provided by prior artcontainers utilising vertically oriented vacuum flex panels.

In a particular embodiment of the present invention, support structures3, such as raised radial ribs as shown, may be provided around thecentral portion 6 so that, as seen particularly in FIGS. 2 and 3, withthe initiator portion 1 and the control portion 2 collapsed, they mayultimately rest in close association and substantial contact with thesupport structures 3 in order to maintain or contribute to top-loadcapabilities, as shown at 1 b and 2 b and 3 b in FIG. 3.

In the expanded views of FIGS. 9 a and 9 b, the steeper angle of theinitiator portion 1 relative to the angle of the control portion 2 isindicated, as is the substantial contact of the support structures 3with the central portion 6 after it has collapsed.

In the expanded views of FIGS. 10 a and 10 b, the support structures 3have been omitted, as in the embodiment of FIG. 5 described later. Alsothe central portion 6 illustrates the steeper angle θ¹ of the initiatorportion 1 relative to the angle θ² of the control portion 2 and also thepositioning of the vacuum panel following its collapse but without thesupport structures or ribs 3.

In a further embodiment a telescopic vacuum panel is capable of flexinginwardly under low vacuum force, and enables expansion from thecollapsed state when the container is uncapped and the vacuum released.

Preferably in one embodiment the initiator portion is configured toprovide for inward flexing under low vacuum force. The control portionis configured to allow for vacuum compensation appropriate to thecontainer size, such that vacuum force is maintained, but keptrelatively low, and only sufficient to draw the vertically foldingvacuum panel section down until further vacuum compensation is notrequired. This will enable expansion from the collapsed state when thecontainer is uncapped and vacuum released. Without the low vacuum forcepulling the vertically folding vacuum panel section down, it willreverse in direction immediately due to the forces generated by thememory in the plastic material. This provides for a ‘tamper-evident’feature for the consumer, allowing as it does for visual confirmationthat the product has not been opened previously.

Additionally, the vertically folding vacuum panel section may employ twoopposing initiator portions and two opposing control portions. Reducingthe degree of flex required from each control portion subsequentlyreduces vacuum pressure to a greater degree. This is achieved throughemploying two control portions, each required to vent only half theamount of vacuum force normally required of a single portion. Vacuumpressure is subsequently reduced more than from prior art vacuum flexpanels, which are not easily configured to provide such a volume ofready inward movement. Again, less stress is applied to the containerside-walls.

Moreover, when the vacuum pressure is adjusted following application ofthe cap to the container, and subsequent cooling of the contents, topload capacity for the container is maintained through side-wall contactoccurring through complete vertical collapse of the vacuum panelsection.

Still, further, the telescopic panel provides good annular strengtheningto the package when opened.

Referring now to FIGS. 5 to 8 of the drawings, preferably in thisembodiment there are two opposing initiator portions, upper initiatorportion 103 and lower initiator portion 105, and two opposing controlportions provided, upper control portion 104 and lower control portion106. When the vacuum pressure is adjusted following application of a cap(not shown) to the container 100, and subsequent cooling of thecontents, top load capacity for the container 100 is maintained throughupper side-wall 200 and lower side-wall 300 contact occurring throughcomplete or substantially complete vertical collapse of the vacuum panelsection, see FIGS. 6 and 7.

This increased venting of vacuum pressure provides advantageously forless force to be transmitted to the side-walls 100 and 300 of thecontainer 100. This allows for less material to be necessarily utilisedin the container construction, making production cheaper.

This allows for less failure under load of the container 100 and thereis no longer any requirement for a vertically oriented panel area to benecessarily deployed in the design of hot-fill containers. Consequently,this allows for the provision of other more aesthetically pleasingdesigns to be employed in container design for hot-fill applications.Further, this allows for a label to be fully supported by total contactwith a side-wall which allows for more rapid and accurate labelapplications.

Additionally, when the cap is released from a vacuum filled containerthat employs two opposing collapsing sections, each control portion 104,106 as seen in FIG. 7, is held in a flexed position and will immediatelytelescope back to its original position, as seen in FIG. 8. There isimmediately a larger headspace in the container which not only aids inpouring of the contents, but prevents ‘blow-back’ of the contents, orspillage upon first opening.

Further embodiments of the present invention may allow for a telescopicvacuum panel to be depressed prior to, or during, the filling processfor certain contents that will subsequently develop internal pressurebefore cooling and requiring vacuum compensation. In this embodiment thepanel is compressed vertically, thereby providing for verticaltelescopic enlargement during the internal pressure phase to preventforces being transferred to the side-walls, and then the panel is ableto collapse again telescopically to allow for subsequent vacuumcompensation.

Although two panel portions 101 and 102 are shown in the drawings it isenvisaged that less than two may be utilised.

Where in the foregoing description, reference has been made to specificcomponents or integers of the invention having known equivalents thensuch equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example and withreference to possible embodiments thereof, it is to be understood thatmodifications or improvements may be made thereto without departing fromthe scope of the invention as defined in the appended claims.

1. A semi-rigid container a side-wall of which has at least onesubstantially vertically folding vacuum panel portion to compensate forvacuum pressure change within the container. 2-15. (canceled)